Disc drives are data storage devices that store digital data in magnetic form on a rotating storage medium on an information storage disc. Modern disc drives comprise one or more rigid information storage discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks typically by an array of transducers (“heads”) mounted to a radial actuator for movement of the heads in an arc across the surface of the discs. Each of the concentric tracks is generally divided into a plurality of separately addressable data sectors. The recording transducer, e.g. a magnetoresistive read/write head, is used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to a host computing system. The overall capacity of the disc drive to store information is dependent upon the disc drive recording density.
The transducers are mounted on sliders or heads via flexures at the ends of a plurality of actuator arms that project radially outward from the actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the transducers move in a plane parallel with the surfaces of the discs.
Typically, such rotary actuators employ a voice coil motor to position the transducers with respect to the disc surfaces. The actuator voice coil motor includes a coil mounted on the side of the actuator body opposite the transducer arms so as to be immersed in the magnetic field of a magnetic circuit comprising one or more permanent magnets and magnetically permeable pole pieces. When controlled direct current (DC) is passed through the coil, an electromagnetic field is set up which interacts with the magnetic field of the magnetic circuit to cause the coil to move in accordance with the well-known Lorentz relationship. As the coil moves, the actuator body pivots about the pivot shaft and the transducers move across the disc surfaces. The actuator thus allows the transducer to move back and forth in an accurate fashion between an inner radius and an outer radius of the discs.
When a stop-start contact disc drive is de-energized, the transducers are automatically moved to a storage location or “park” location on the disc surfaces. The park location is typically adjacent and outside the inner or outer periphery of the data storage region of the disc and is typically called a landing zone. This landing zone typically does not contain any useable data as the transducer physically contacts the disc at rest. Consequently, any data stored in this area would likely be lost or compromised. In addition, the landing zone is typically roughened to minimize the stiction of the transducer against the disc surface.
Alternatively, disc drives may utilize load/unload ramps to facilitate removal of the transducers from the discs to a parked position adjacent the discs. The load/unload ramps in a disc drive are typically stationary, such that in the process of the suspension assemblies being unloaded from the disc, the transducers are moved to the outer rim portion of the discs and onto ramps which extend over the outer rim portions of the disc. The transducers then traverse up the load/unload ramps to a park location off of the disc surfaces. In the reverse process, the transducers are loaded onto the disc by the transducers moving down the stationary ramps onto the media.
The use of a load/unload ramp to store the transducer under de-energized conditions has several advantages over the use of the traditional landing zone on the disc surface. First, using a load/unload ramp eliminates stiction concerns and friction failures associated with the transducer being de-energized on the landing zone of the disc. Second, information storage disc have a protective carbon overcoat which is at least in part required to support the transducer-landing zone interaction. In the absence of this interaction, a thinner carbon overcoat may be utilized on the disc surface. A thinner carbon overcoat on the information storage disc allows for the design of decreased transducer-to-disc media spacing and for corresponding increased recording density. Finally, by parking the transducer head off the information storage disc surface on the load/unload ramp, a larger amount of disc space is available for data storage, which results in increased recording density.
However, the use of a load/unload ramp in a disc drive has several disadvantages, one of which is that the numerous interactions between the load/unload ramp and transducer/suspension assembly presents a tribological problem involving friction, lubrication and wear on the surfaces of both the load/unload ramp and transducer/suspension assembly. Ultimately, the level of friction between the surfaces of the load/unload ramp and transducer/suspension assembly determines the wear on those surfaces and ultimately to the formation of debris off of those surfaces and into the disc drive. Debris formation inside the disc drive is a major concern in the disc drive industry. Thus, minimizing friction between the load/unload ramp and the transducer/suspension assembly is a major concern in the disc drive art.
Presently, friction between the load/unload ramp and transducer/suspension assembly is minimized by forming the ramp out of a low friction-low wear plastic and by lubricating the transducer/suspension assembly or more preferably the load/unload ramp with a Teflon™ based lubricant. However, administering the proper amount of lubricant on the load ramp surfaces and of manufacturing a cost effective load/unload ramp with a lubricant film continues to present shortcomings in disc drive art. Against this backdrop the present invention has been developed.